Despite his decision, Glendening urged Marylanders not to panic and said there is no reason to avoid going out on the Chesapeake Bay or eating bay seafood.

He said he and his family will be out on the water, and "I plan to eat Chesapeake Bay seafood this weekend."

Dr. Glenn Morris of the University of Maryland Medical System headed a team of doctors from his hospital and Johns Hopkins hospital who examined 13 watermen and state employees who complained of various health problems after coming into contact with the water in the Pocomoke River or with dead or dying fish.

Seven of them experienced mild memory loss, similar to a mild concussion, that could not be explained by any medical causes other than exposure to a waterborne toxin, Morris said.

Dr. Martin Wasserman, state health secretary, said the medical team cannot say for sure that the health problems, which also included skin rashes and respiratory problems such as wheezing, were caused by toxins released by pfiesteria piscicida or a similar one-celled organism.

But he said there is "a likely link between pfiesteria and people working on the river."

Tests were not completed on two of the 13 people examined last week. In other cases, the medical team found other possible causes of the symptoms, but did not rule out pfiesteria as a cause.

JoAnn Burkholder, a North Carolina State University researcher who first identified pfiesteria, concurred with Glendening and other state officials that there is no danger in eating seafood and no reason to avoid any areas of the bay or its tributaries other than the Pocomoke.

The order prohibits any activities on the closed section of the river except that boaters can pass through from the upper Pocomoke to the Pocomoke Sound.

Ray Feldmann, a spokesman for Glendening, said there is no timetable for reopening the river. He said it will be reopened when there is a consensus that there is no further danger to health.

Randolph Gordon, Virginia Health Department director, said the fish kill appears to be waning in Virginia waters and no fish were seen on top of the water Friday.

Earlier this month, part of the river was closed for nearly a week when some 11,000 fish mysteriously died on a stretch of the lower Pocomoke. Scientists suspect that the large kill detected Aug. 6 is linked to pfiesteria piscicida.